Taphonomy of salt marsh foraminifera: an example from coastal Georgia

Abstract

In salt marshes of St. Catherines Island, Georgia, total foraminiferal density decreases significantly within the top 10 cm of marsh sediment. Selective preservation impacts both calcareous and agglutinated taxa; calcareous taxa are removed through dissolution and agglutinated ones through bacterial degradation of cements or predation. Shallow to deep infaunal taxa generally are the most likely to be preserved, although Miliammina fusca and Ammotium spp., all epifaunal to shallow or intermediate infaunal dwellers, have cements that are highly susceptible to degradation in southeastern U.S. marshes. Total foraminiferal density in both surface and subsurface sediment is higher in the low marsh than either the transitional or high marsh zones. Selective preservation and downcore enrichment by some infaunal taxa alters the percent abundance of some paleoenvironmentally significant taxa in subsurface assemblages. The best baseline for paleoenvironmental studies using salt marsh foraminifera in these settings is not the marsh surface (0–1 cm), but rather assemblages preserved ∼10 cm below the marsh surface.